245 to 265 Computer Recal

Has anyone switched from 245/75 16 to 265/75 16 and had the dealer recalibrate the computer. I would guess they could since both sizes are available from the factory. I have a 2003 1500 4x4 with a 4.8, and switched for 245 to 265. The dealer claims the calibrations are the same, so no need to recalibrate. I don't buy it, and my speedo is now off by about a mile every 30 miles. This has afffected my DIC, fuel computer, etc. Any help is appreciated.

You are right. It is not the same calibration, and they can adjust for factory tire Sizes. This is what my dealer told me when I went from 245s to 315s. They were not able to help me because 315s aren't factory.

Yes, it does need to be recal. When I went to my 17s and low pros, I used my superchips tuner to recal my computer for this. I would suggest going to another dealer if your current one won't do it. If the dealerships won't help you out, and you really want to fix this problem, I would suggest a unit such as The JET SCU 2000 (Speed Control Unit). This is a fairly inexpensive unit that does no more than allow you to set the computer for tire/gear changes, shift points, and removes the speed limit governor. It doesn't effect the air/fuel ratio such as other programmers, just a device made for applications such as yours( that's why its considerably cheaper).

http://www.martelbrothers.com/frame.php?mainsrc=http://www.jetchip.com/domestic/default.cfm